1. Field of the Invention
The present invention relates to a composite yarn for technical or industrial use, which can be assembled into all types of textile structures, especially suitable textile surfaces, in order to meet any particular application or specification, for example for the manufacture of blinds or curtains.
2. Description of Related Art
In the prior art, document U.S. Pat. No. 4,127,698 discloses the production of fire-retarding composite fibers comprising a mixture of two fibers. The first, termed the matrix fiber, is based on PVC and partially acetalized PVA and furthermore includes an inorganic fire retardant consisting of a hydrated tin oxide and a hydrated antimony oxide. The second fiber is based on polyester, acrylic or cotton.
Document EP-A-0,385,025 describes the manufacture of a composite yarn comprising a core made of glass fibers and a sheath obtained by spinning low-melting-point fibers, for example cotton fibers.
However, these documents essentially relate to yarns obtained by spinning mixtures of fibers and are not appropriate to the applications envisaged below.
Moreover, high-performance composite yarns are already known, which the Applicant manufactures and sells, comprising:
a core composed of a continuous yarn, for example a glass yarn; PA1 and a coated sheath composed of a plastic matrix consisting of at least one chlorinated polymer material, for example a polyvinyl chloride; PA1 a fire-retarding inorganic filler incorporated into and distributed within said matrix; PA1 and a plasticizer.
Preferably, but not exclusively, such a yarn is obtained by coating the core with a plastisol comprising the chlorinated polymer material, for example polyvinyl chloride, and the plasticizer, and then by gelling the plastisol around the core.
High-performance woven fabrics obtained from such yarns, when they are employed in various environments, especially for fitting out both the interior and exterior of properties or constructions, for example as blinds, are subject to fire-behavior requirements defined by national or international homologation or authorization procedures and/or regulations.
Thus, the regulations applicable to such woven fabrics in the Federal Republic of Germany define various classes which are characterized especially by the length of the specimen destroyed by fire and by the temperature of the combustion smoke and are identified by the letters B1 to B3, the letter B1 characterizing the best fire behavior attainable by a material comprising organic matter.
As regards the regulations applicable in France, these also define various classes which, on the one hand, are characterized especially by the emission of smoke and identified by the letters F0 to F5, F3 being the best behavior attainable by a material containing a halogenated polymer, and which, on the other hand, are characterized especially by the residual ignition temperature of the woven fabric and are identified by the letters M0 to M4, the letter M1 identifying the best fire behavior generally attainable by a material comprising organic matter.
At the present time, high-performance woven fabrics obtained from the composite yarns defined above have a certain limitation in terms of their fire behavior, this limitation being illustrated by the fact that such woven fabrics have never been able, without a chemical treatment after they have been woven, to achieve the B1 classification of the German regulations together with the M1 classification of the French regulations.
The main reason for the limitations mentioned above obviously stems from the organic nature of certain constituents of the composite yarn, especially the chlorinated polymer material and the plasticizer, or indeed certain coating additives.
Various attempts have been made to improve the intrinsic fire behavior of these composite yarns, for example by using special plasticizers such as organic phosphates. Unfortunately, by using such plasticizers the processing characteristics (flexibility, gliding power, etc.) of these yarns suffer, which impairs their subsequent weaving and makes the latter more difficult. Moreover, the incorporation of such plasticizers increases the smoke index.
Nor is it possible to increase the proportion by weight of the fire-retarding filler significantly, except, as previously, to the detriment of the processing characteristics of the composite yarn.
With regard to the performance of the fire-retarding filler proper, various documents have proposed different kinds of compounds or compositions capable of improving the fire behavior of the plastic matrices into which the fire-retarding filler is incorporated, but without the application or forming of the fire-retarded plastic, for example into a yarn, being specified.
Thus, in the case of a matrix based on polyvinyl chloride, document JP-A-58,185,637 has proposed a fire-retarding filler comprising a chlorinated polyethylene, a compound chosen especially from antimony and aluminum oxides and/or hydroxides, and preferably another compound chosen from certain zinc salts, including zinc borate.
Again, in the case of a matrix based on polyvinyl chloride, which also incorporates a stabilizer, a plasticizer consisting of a phosphoric ester, and an alumina hydroxide filler, document FR-A-2,448,554 has proposed a fire-retarding filler comprising an antimony oxide, optionally combined with a zinc borate.